This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Retrospective Data Collection Study in Patients Receiving Dexamethasone Intravitreal Implant (Ozurdex®) for Macular Oedema Due to Retinal Vein Occlusion (RVO) (NCT01445626), a registered phase not stated study. The primary outcome is Time to OZURDEX® Re-injection.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01445626 |
| Phase | Phase not stated |
| Condition | Macular Edema |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 87 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Allergan |
| Results posted | Yes |
2. Clinical Question
Population
Patients with macular oedema due to retinal vein occlusion who received at least two OZURDEX® injections. The registry record lists an enrollment of 87 and describes the analysis population for the primary outcome as participants with data available for analysis.
Intervention
Dexamethasone intravitreal implant 0.7 mg, identified in the record as OZURDEX®. The study concerns patients who received repeated injections in routine clinical care, rather than assignment to a treatment within a randomized comparison.
Comparator
No comparator group is described. The record identifies a single group of all participants, and the allocation is not stated. The study therefore does not provide a like-for-like control comparison.
Primary question
What was the time, in days, between the first and second OZURDEX® injections, up to 12 months? The endpoint is specified as a mean with standard deviation, but its numerical result is not reported in the registry record.
The clinical question is descriptive: among the eligible patients whose records contributed data, what interval separated the initial injection and the next injection? The study summary also identifies efficacy, safety, and re-injection interval as areas of interest. Listed secondary outcomes concern visual acuity, retinal thickness measured by optical coherence tomography, and time to visual-acuity improvements.
Because the record describes retrospective data collection and no comparator, the question is not whether treatment outperformed another treatment or no treatment. It is also not a randomized estimate of a treatment effect. The observed interval, if reported, would describe the care and records represented in this cohort; it would not by itself establish why re-injection occurred when it did. The registry record does not report the primary outcome value, the number with available primary-outcome data, or numerical results for the listed secondary outcomes.
3. Trial Design
This is a completed retrospective data collection study sponsored by Allergan. The registry title and summary identify patients receiving dexamethasone intravitreal implant (OZURDEX®) for macular oedema due to retinal vein occlusion. The study began in 2011-10, and primary completion is recorded as 2012-01. Enrollment is listed as 87.
The participant description is important for understanding the design: all participants had received at least two OZURDEX® injections. This is a cohort selected on the basis of treatment already received, not a comparison created through random assignment. The registry record does not state how participants were identified, how many records were screened, what eligibility criteria beyond the injection history were applied, or how missing clinical records were handled.
The primary outcome is the time in days from the first to the second injection, with a timeframe of up to 12 months. It is specified as a continuous measure summarized by a mean and standard deviation. The registry lists secondary outcomes involving change in best corrected visual acuity, visual-acuity improvement thresholds, central retinal thickness by optical coherence tomography, and time to visual-acuity improvement. The registry count of outcome measures is 7.
No randomized allocation or control arm is described; allocation is not stated in the record. The group is identified as all participants. The registry record reports no analysis entries. It also does not report a protocol, a statistical analysis plan, a sample-size justification, or details of data abstraction and quality checks. Consequently, the study design can be described as retrospective and single-group from the available information, but its operational details and the analyses actually performed cannot be reconstructed from the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | All Participants |
|---|---|
| STARTED | 87 |
| COMPLETED | 87 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: All participants with data available for analysis.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | All Participants |
|---|---|---|
| Participants analysed | 87 | |
| Age Continuous | Years | 68.48 (SD 9.15) |
| Sex: Female, Male: Female | Participants | 29 |
| Sex: Female, Male: Male | Participants | 58 |
6. Primary Endpoint
The registry lists the primary outcome as Time to OZURDEX® Re-injection, measured over Up to 12 months.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | Days |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the time in days between the first and second OZURDEX® injections. The stated timeframe is up to 12 months, and the analysis population is all participants with data available for analysis. The endpoint is summarized using a mean and standard deviation.
Re-injection interval is a clinically relevant description of treatment patterns because it records how much time elapsed before a subsequent injection in this cohort. It is not a direct measure of visual benefit, retinal thickness, or safety. Those topics appear separately among the listed secondary outcomes. The interval also does not, on its own, identify the reason for re-injection or establish that the timing was caused by the implant. Decisions may be influenced by clinical circumstances and care practices, but the registry record does not describe those factors.
For a continuous endpoint, the mean gives a measure of the central value of the observed intervals. The standard deviation describes how dispersed individual intervals are around that mean. A mean alone would not show whether most intervals were close to one another or whether values varied widely. The registry record specifies this summary approach but does not report the mean, standard deviation, endpoint-specific denominator, or a confidence interval. The primary endpoint’s numerical result is therefore not available for interpretation from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the study question and design but does not provide the numerical primary outcome result. Although time to re-injection is defined as the number of days between the first and second injections, the mean and standard deviation are not reported in the registry record. The number of participants with data available for that analysis is also not reported. It is therefore not possible to describe the observed average interval, its variability, or the precision of an estimate from the record.
The listed secondary outcomes address visual acuity and retinal thickness, including changes from baseline and time to specified visual-acuity improvements. Their titles describe what was intended to be assessed, not what was observed. Numerical results for these outcomes are not reported in the registry record. A listed outcome should not be read as evidence that a particular change occurred.
The safety entries have some numerical detail: the record lists 6 participants with serious adverse events among 87 at risk and 47 with other adverse events among 87 at risk. Serious adverse event terms listed include cataract operation at 3.4%, suspected glaucoma at 1.1%, choroidal detachment at 1.1%, and cataract progression at 1.1%. These entries describe reported events in the cohort. They do not establish that the implant caused them, and they cannot be compared with an untreated or alternative-treatment group because no comparator is described.
There is no randomized comparison, and the study includes patients who had already received at least two injections. The observations are consequently descriptive of a selected group and do not isolate the effect of treatment from other influences. The registry record does not report adjustment for confounding, a prespecified statistical analysis plan, confidence intervals, or inferential tests. The record reports 0 analysis entries, so it does not provide a documented statistical analysis to assess alongside the outcome definitions.
These limitations do not make the recorded information meaningless: it identifies the population, the endpoint definitions, and some safety counts. They do constrain interpretation. Without reported outcome estimates, uncertainty measures, and analysis details, no conclusion about the magnitude or precision of the primary or secondary outcomes can be drawn from the registry record.
9. Statistical Methods Explained
The registry identifies a continuous primary measure, an analysis population, and a summary statistic. It does not report the resulting estimate or a detailed analysis plan. The explanations below describe general statistical principles; they should not be taken as claims about methods used in this study unless the registry record explicitly says so.
What does a mean describe?
For a continuous measure such as elapsed time, the mean is the arithmetic average of the observed values in the analysis set. It provides one summary of the center of a distribution. The mean can be affected by unusually short or long intervals, so it is most informative when considered alongside a description of spread and the shape of the data. The registry specifies the mean for the primary endpoint, but the numerical mean is not reported in the registry record.
What does the standard deviation add?
As a general statistical concept, the standard deviation describes how far observations tend to lie from their mean. A smaller standard deviation indicates that observations are more clustered around the mean; a larger one indicates more variability. It is a description of individual-level spread, not a measure of how precisely the mean has been estimated. Precision of an estimate is commonly conveyed with a confidence interval, but a confidence interval for the primary endpoint is not reported in the registry record.
The mean and standard deviation can be useful for summarizing a distribution that is reasonably represented by those statistics. If intervals are markedly skewed or contain influential extreme values, the mean may not represent a typical participant’s interval well. The registry record does not report the distribution, a median, quantiles, or diagnostic checks, so the suitability of the specified summary cannot be assessed from the record.
How should a confidence interval be understood?
In general, a confidence interval expresses the statistical uncertainty around an estimated quantity under the assumptions of the analysis. It is not a range containing a known proportion of individual observations, and it does not correct bias from selection, measurement, or confounding. No confidence interval for the primary endpoint is reported in the registry record. Without an estimate and a measure of uncertainty, the precision of the re-injection interval cannot be evaluated.
What would a comparison require?
A treatment comparison aims to distinguish differences associated with treatment from differences that would have occurred for other reasons. Random assignment can help create comparable groups, while observational analyses may use adjustment for measured differences; neither approach removes every possible source of bias. This record describes one group and does not identify a comparator. The registry record does not report a comparative treatment-effect estimate or adjustment strategy. Thus, the outcomes are not evidence of a contrast against another treatment or against no treatment.
How should the planning illustrations be read?
In general, a sample-size calculation estimates how much information a future study might need under specified assumptions. Such a calculation is a planning illustration, not an observed result and not observed power. The stated assumptions for the planning illustrations are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. Time-to-event illustrations use the total number of events, while other illustrations use participants per arm. These assumptions do not describe the design of this retrospective single-group study. The underlying observed effect is not reported in the registry record, so the planning illustrations cannot be independently interpreted from the record alone.
General methods for time-to-event outcomes often account for the timing of events and for observations where the event time is not fully observed. However, this primary endpoint is specifically summarized as a mean and standard deviation, and the registry record does not report a time-to-event model, censoring rules, or an alternative analysis. Those methods should not be assumed to have been used.
Why can over-dispersion matter?
As a general concept, over-dispersion occurs when the variability in data is greater than a statistical model assumes. If a model underestimates variability, its standard errors can be too small and its confidence intervals too narrow. This can make results appear more precise than they are. Over-dispersion is particularly relevant to some count-data models; the registry does not identify such a model for this study. The record also does not report a model, a dispersion assessment, or any adjustment for over-dispersion, so no claim about its presence or handling is justified.
Overall, the registry gives a definition and intended summary for the primary endpoint, but not the numerical data or enough analysis detail to reproduce or evaluate an estimate. General statistical principles help explain what the stated mean and standard deviation would convey, but they cannot supply the missing result or establish how the study’s analyses were conducted.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary outcome and secondary outcomes concerning visual acuity, retinal thickness, and time to improvement. When a study examines multiple outcomes or multiple contrasts, the chance of at least one apparently unusual result can increase if each is tested separately without accounting for multiplicity. General approaches include prespecifying a hierarchy, adjusting significance thresholds, or treating secondary findings as exploratory. The registry record does not report whether any multiplicity strategy was planned or used. It also does not report numerical results or tests for the listed outcomes.
Missing data can affect both the composition of an analysis population and the interpretation of its results. The primary outcome population is described as all participants with data available for analysis, but the number with available data is not reported. The record does not state how missing dates, incomplete records, or missing secondary outcome measurements were handled, or whether any sensitivity analysis was conducted. Because data collection was retrospective, completeness and consistency of historical records are relevant considerations; the registry record does not describe procedures for addressing them.
The record reports 0 analysis entries. It does not provide a statistical analysis plan, details of outcome-specific analysis populations, or a sample-size justification. These absences mean it is not possible to determine whether analyses followed a prespecified plan, how multiplicity was considered, or how missing observations affected estimates. No assumptions about those choices should be inferred from the outcome list alone.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| All Participants | 6 | 87 | 6.9% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| All Participants | 47 of 87 |
Most frequent serious adverse event terms
| Event term | Organ system | All Participants |
|---|---|---|
| Cataract operation | Eye disorders | 3 of 87 |
| Suspected glaucoma | Eye disorders | 1 of 87 |
| Choroidal detachment | Eye disorders | 1 of 87 |
| Cataract progression | Eye disorders | 1 of 87 |
Most frequent non-serious adverse event terms
| Event term | Organ system | All Participants |
|---|---|---|
| Intraocular pressure increased | Investigations | 16 of 87 |
| Glaucoma | Eye disorders | 10 of 87 |
| Eye laser surgery | Eye disorders | 9 of 87 |
| Cataract operation | Eye disorders | 6 of 87 |
| Retinal degeneration | Eye disorders | 6 of 87 |
Serious events with the highest arm-level rate: cataract operation (3.4%), suspected glaucoma (1.1%), choroidal detachment (1.1%), cataract progression (1.1%).
The registry lists 6 participants with serious adverse events among 87 at risk and 47 participants with other adverse events among 87 at risk. These are separate safety categories as reported in the record. They should not be added together: a participant may have experienced more than one event or may appear in more than one category, and the record does not clarify overlap. The counts are not estimates of risk attributable to treatment.
The serious adverse event terms listed are cataract operation at 3.4%, suspected glaucoma at 1.1%, choroidal detachment at 1.1%, and cataract progression at 1.1%. These percentages are quoted as recorded. The record does not give further details on timing, event-level counts, severity grading, adjudication, or causal assessment for these terms. The death count is not reported in the registry record; a missing count should not be interpreted as zero.
Safety events recorded in a treated cohort can describe what was reported during the study, but a single-group retrospective record cannot establish whether treatment caused an event or whether its occurrence differed from another care strategy. The registry record does not identify a comparator, so these figures do not support a comparative safety estimate.
12. What the Result Does, and Does Not, Mean
This study addresses a useful descriptive question: how much time elapsed between the first and second dexamethasone intravitreal implant injections among the included patients with macular oedema due to retinal vein occlusion. It also identifies visual-acuity, retinal-thickness, and safety outcomes of interest. The registry record makes the population and endpoint definitions visible, but does not report the primary endpoint estimate or numerical results for the listed secondary outcomes.
Accordingly, the record does not establish the average re-injection interval or how much that interval varied. It does not show the size or precision of changes in visual acuity or central retinal thickness. Listing an outcome is not the same as reporting a result, and no direction or magnitude of change can be inferred from an outcome title.
The safety counts and serious-event terms document reported events in the study group. They do not demonstrate causation. Without a comparator, the record cannot show whether the observed events were more or less frequent than they would have been under another treatment or no treatment. Retrospective selection of patients who received at least two injections also means the cohort should not be taken as representative of every person who might receive the implant.
In general, a result can be statistically precise yet still be affected by selection or confounding; conversely, a descriptive result can be useful without proving a causal effect. Here, the numerical primary result and its uncertainty are not reported, limiting even descriptive interpretation of the central endpoint. The registry record therefore supports understanding what the study intended to describe and which safety information it recorded, but not a conclusion about treatment efficacy, comparative safety, or the causes of observed outcomes.
13. Why This Trial Matters Statistically
Retrospective studies can describe patterns of care and outcomes in patients treated outside a randomized comparison. Re-injection timing is one such pattern: it links the initial injection to a subsequent injection and can help characterize treatment intervals in the records under study. Clearly defining the interval, the eligible population, and the available-data analysis set is statistically important because each affects what an estimate represents.
This record makes several of those definitions explicit. It identifies a cohort of patients who received at least two injections, defines the primary interval as the days between the first and second injections, and specifies a mean and standard deviation as the summary. It also names secondary outcomes and reports safety counts. These details can help readers distinguish the endpoint being studied from the broader clinical topics of efficacy and safety.
The record also illustrates why outcome definitions should be separated from outcome results. A registry may describe what was intended to be measured without giving numerical estimates. Here, the primary numerical result and secondary outcome values are not reported in the registry record, so the clinical question cannot be answered quantitatively from the record. A completed status does not fill that gap.
The absence of a comparator is equally important. Descriptive observations can characterize a treated cohort, but they do not isolate a treatment effect. Retrospective inclusion based on receiving repeated treatment may further limit how broadly the cohort represents patients outside the study. The record’s value is therefore in clarifying the design, endpoints, and reported safety observations while also showing the limits of what can be inferred without outcome estimates, uncertainty measures, and comparative analyses.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The primary limitation for interpretation is that the registry record does not report the mean time to re-injection, its standard deviation, or a confidence interval. The endpoint-specific number of participants with available data is also not reported. Without these details, neither the observed interval nor its precision can be described.
The study is retrospective and has no comparator group described. Allocation is not stated, and the record identifies a single group of all participants rather than a like-for-like control comparison. Differences in patient characteristics, clinical decisions, or care settings cannot be separated from treatment using the information reported. The record does not describe confounder adjustment.
Eligibility is tied to having received at least two injections. This selection may limit the relevance of the cohort to patients who did not proceed to a second injection. The record does not explain how the cohort was assembled, the number of records screened, or reasons for exclusion. It also does not report the data sources, abstraction procedures, or consistency checks used in this retrospective collection.
Numerical results for the listed secondary outcomes are not reported in the registry record. Missing-data methods, multiplicity handling, and a prespecified analysis plan are also not reported. Safety information includes event counts and selected terms, but the death count and details needed to assess event timing or attribution are not reported in the registry record. Together, these omissions limit assessment of completeness, bias, precision, and reproducibility.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Retrospective Data Collection Study in Patients Receiving Dexamethasone Intravitreal Implant (Ozurdex®) for Macular Oedema Due to Retinal Vein Occlusion (RVO) — NCT01445626.
- Registry record last updated 2013-02-18; status last verified 2013-01.
- Results first posted 2013-02-18.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
The registry describes a completed retrospective data collection study sponsored by Allergan of patients receiving dexamethasone intravitreal implant 0.7 mg for macular oedema due to retinal vein occlusion. Enrollment is 87; the study began in 2011-10, with primary completion in 2012-01. Participants had received at least two injections.
The primary outcome is the time in days between the first and second injections, up to 12 months, summarized as a mean and standard deviation. Numerical primary and secondary outcome results are not reported in the registry record. The record lists 6 participants with serious adverse events and 47 with other adverse events, each among 87 at risk; selected serious-event terms are also reported. No comparator is described, and the record reports 0 analysis entries.